Ferguson police
Police officers keep watch while demonstrators (not pictured) protest the death of black teenager Michael Brown in Ferguson, Missouri, Tuesday, Aug. 12, 2014. Reuters

FERGUSON, Mo.--After more than a week of tension and spurts of unrest, Ferguson security forces moved to break up a crowd of marchers Monday night by driving armored vehicles down the street, blaring a high-pitched siren designed to disperse crowds. No violence appeared to be taking place when the forces moved down the street. Cops refrained from shooting tear canisters and rubber bullets, as they have done several times in the past week.

The scene in Ferguson had remained mostly peaceful through the evening until the armored tanks aggressively moved through the streets, forcing protesters down the street. And, local religious leaders with megaphones tried to convince protesters to move away and back up from their positions to let the tanks pass.

Later, on Monday night, about two dozen police officers in riot gear had spread out in front of a QuikTrip store where about 150 protesters remain despite instructions from police, who showed restraint in the face of at least one incident of bottle-throwing by a protester.

Although the cause of the aggressive behavior by the police was not immediately clear, it appeared that protesters throwing water bottles angered the security forces on the front line. CNN reported that two men had thrown bottles or jugs of a pink liquid and were arrested.

"I hate the police but I wouldn't do something like that," Demetrius Tressell, 24, said.

By 10 p.m. the crowd had moved back from its original position and police ranks doubled.

Malik Shabazz, an attorney with the Black Lawyers for Justice, blamed provocateurs for sparking the confrontation.

As tense as the standoff was, both sides appeared to exercise restraint in order to keep the event from spinning out of control. The protestors had been told earlier that they were free to march but needed to keep walking and not stop to gather. The security forces, in their turn, relied on an ear-splitting siren and a slow drive through the middle of the crowd to quell any further action by protestors.

As the crowd began to disperse, the police announced, "Continue all of your peaceful actions and thank you for your cooperation."